The CHECKand INITblocks run when compilation is complete,
but before the program starts. CHECK can mean
"checkpoint,"
"double-check," or even just
"stop." INIT
stands for "initialization." The
difference is subtle: CHECK blocks are run just
after the compilation ends, whereas INIT blocks
are run just before the runtime begins (hence, the
-c command-line flag to Perl runs up to
CHECK blocks but not INIT
blocks).

Perl calls these blocks only during perl_parse( ),
which mod_perl calls once at startup time. Therefore,
CHECK and INIT blocks
don't work in mod_perl, for the same reason these
don't: